Epoxy compounds, which are manufactured in a great variety on large industrial scales throughout the world, are used for an extensive scale of end applications, such as the manufacturing of shaped articles, including embedded small electronic components such as semi-conductors or chips and the prepregs for the subsequent manufacture of printed circuits for the electronic industry, coatings including the organic solvent based coatings as well as the more modern aqueous epoxy resin dispersion coatings, and in particular can and drum coatings, composites and laminates showing great flexibility, and the like.
Said starting epoxy compounds were manufactured up to now by means of the starting reagent epihalohydrin and in particular epichlorohydrin, which in its turn was manufactured via allylchloride, prepared from propene and gaseous chlorine.
It will be appreciated that on the one hand, there has been developed in the last decade and in particular in the last five years, an increasing pressure from national or regional governmental regulations and requirements to chemical process industry, in order to drastically reduce possible chlorine emissions or even to avoid the use of chlorine completely, and on the other hand, in the current manufacturing processes for chlorination of propene in the gaseous phase there is still a need to improve the relatively low yield and to diminish the high fouling tendency.
Moreover, during the reaction of epihalohydrin with phenolic compounds to form epoxy resin it is not possible to avoid completely that halogen, originating from the epihalohydrin, is intermingled in a resin as a product in the form that the halogen atom is chemically bound to the epoxy resin itself. As one of the important applications of the epoxy resin is encapsulation of micro electronic material, it will be appreciated that this intermingled halogen liberates as an acid by moisture, during use of the final article for a long period of time and this acid leads to corrosion of a metal material.
Therefore one object of the present invention is formed by a process, meeting the requirements of the present environmental legislation and that one presumably enforced in the near future, and starting from cheap and generally available basic chemicals.
One of the alternative manufacturing routes for epoxy resins, proposed in the past was that according the following simplified reaction scheme: ##STR4## transesterification with e.g. alkylene carbonate (C.sub.1 -C.sub.4 alkyl), cycloalkylene carbonate, arylalkylene carbonate or dialkylene carbonate (C.sub.1 -C.sub.4 alkyl) and preferably propylene carbonate+alkyleneglycol, cycloalkylene glycol or arylalkylene glycol, and preferably propylene glycol, wherein R.sub.1 represents a residue comprising one or more additional phenol groups, wherein R.sub.2 represents a residue comprising one or more additional groups of the formula: ##STR5## wherein R.sub.3 represents a residue comprising one or more additional groups of the formula: ##STR6## and wherein R.sub.4 represents a residue comprising one or more additional groups ##STR7##
Although it was already known from e.g. Japanese patent application Sho 61-33180 A, to produce epoxy compounds by decarboxylating a carbonate compound, using as catalyst a combination of an alkali metal halide and of a dihydrogenphosphate of an alkali metal while earlier proposed similar processes were known from e.g. JP-Sho-57-77682 A and U.S. Pat. No. 2,856,413, said route could not be used for economical manufacture of epoxy compounds up to now.
In particular from JP-Sho-61-33180 it will be appreciated that the finally obtained mono-epoxy compounds had such a simple molecular structure, that they could be recovered from the initially crude reaction mixture by distillation.
However such a distillation has appeared to be not possible for the commercial standard difunctional and multifunctional epoxy compounds aimed at.
Therefore there was still a strong need for improvement of this proposed route to enable industrial scale manufacture at all.